Scotland Yard's adoption of deliberately anti-confrontational tactics at the "March for the Alternative" appeared, initially, to have paid off.

Despite the bigger than expected turnout and a palpable sense of frustration among many participants over the scale of spending cuts, the Metropolitan police's deliberate "softly, softly" strategy appeared to have helped discharge early tensions.

News of the first arrest did not surface until almost three hours after the march began, at 2pm, after several hundred protesters attacked Topshop on Oxford Street with paint bombs, smashing windows. Later, anarchists targeted the Ritz hotel.

More than 4,500 officers were on duty while two helicopters monitored splinter groups that deviated from the main march route. Overall, the strategy remained one of "passive policing". Offices in riot uniform, mounted units and armoured vehicles were kept in reserve, to be deployed only in the event of large-scale disorder.

Then came the occupation of Fortnum and Mason in Piccadilly. At least 30 riot vans descended on the street and began kettling, prompting violent clashes. A stand-off developed as the crowd were pushed back on to Piccadilly Circus. By nightfall fireworks, flares and stakes were raining down on police lines. One group just 100 yards away in a side street managed to build a large barricade of scaffolding and set it on fire. It took several minutes for the first riot police to appear.

Commander Bob Broadhurst, who was in charge of the policing operation, had vowed to keep "containment" to a minimum. The day before the march, the Yard's public order unit had been criticised by the parliamentary joint committee on human rights, which concluded there was "considerable room for improving" frontline officers' understanding of guidelines on the use of kettling.

Last year, during tuition fee protests large numbers of demonstrators had been confined by police for hours. This time, although reports emerged of "light kettling", officers appeared intent on keeping the huge crowd moving.

The Met's new tactic for dealing with protests appeared to have paid off when, by 8.30pm, most of the crowd had drifted away. Officers managed to avert large-scale disorder and apart from a sequence of incidents around Piccadilly during the early evening, Broadhurst would have been satisfied.

On the eve of the march, the Met had promised a more enlightened use of kettling if it was required, using observers to release protesters not deemed to be a public order threat.

The cross-party committee had also said it was "surprised" that there was no specific guidance on the circumstances in which police may be justified in using batons on the heads of protesters. Dozens of demonstrators alleged they were struck on the head by officers during the student protests before Christmas.

Throughout the planning for the anti-cuts march, Broadhurst and the Yard's public order unit will have been all too aware of what can happen when a protest goes wrong. The inquest into the death of 47-year-old Ian Tomlinson, who died after being struck by a police officer during the G20 protests in April 2009, begins on 28 March.

It is expected to hear detailed criticism of police operations, planning and command during the demonstration.

Broadhurst must have known the Yard cannot afford another fatality at a public protest.